In the fields of civil engineering and construction, in order to build a soil structure to be used as a structure like a retaining wall which is built in a foundation constructing work, (i) an H-shaped steel or the like, which is to serve as a support body (core) for supporting from inside a hardened body of a hydraulic composition formed by hardening the hydraulic composition such as cement milk or freshly mixed concrete, is preparatorily loosely inserted into a bore hole and the hydraulic composition such as cement milk or freshly mixed concrete is poured to around the H-shaped steel so as to be hardened (hydrated), or alternatively (ii) an H-shaped steel or the like as core is buried (driven) into a hydraulic composition which has been poured into a bore hole and thereafter the hydraulic composition is hardened (hydrated).
Examples of such building techniques include a peristylar soil cement continuous wall technique which is recently generally used for civil engineering works and construction works for high-rise building construction and such works in river and underground areas. In this technique, areas surrounding a construction site are bored and holes obtained by the boring are filled with a cement composition such as a soil cement milk so that soil cement walls for suppressing hydraulic pressure and earth pressure are constructed, in which H-shaped steels, for example, are used as cores. In earth retaining works as well, support bodies (cores) such as H-shaped steels are buried in a cement-based substance so as to form concrete walls.
Support bodies such as H-shaped steels thus buried in hydraulic compositions are in many cases unnecessary after finishing of the construction, and if the support bodies unnecessary are extracted from the hardened bodies of the hydraulic composition and collected so as to be re-used, it will be of advantage, from the viewpoints of saving of resource and environmental safeguards, and also will be very economical. Further, by extracting from the hardened bodies of hydraulic composition the support bodies which have become unnecessary after foundation constructing works finished, or separating portions of the hardened bodies in contact with the support bodies from the support bodies or removing the same therefrom, it will facilitate such secondary works as the expansion and the remodeling of existing buildings and the construction of sewerage systems and water supply systems.
Therefore, the support bodies such as H-shaped steels buried in the hydraulic composition are preferably extracted from the hardened bodies (hydrates) after the hardening of the hydraulic composition so as to be re-used, or are preferably extracted from the hardened bodies and removed, or made separable therefrom, so that they will not later obstruct redevelopment of the underground of the same site.
The support bodies (cores) thus buried and the hardened bodies of the hydraulic composition firmly bond with each other, and in order to separate the support bodies from the hardened bodies of the hydraulic composition and extract them, such a considerably great pulling force that may overwhelm bond strength (adhesive strength) is required (in many cases, extraction is impossible), resulting in that extra equipments, costs, and time for the separation are needed. As a result, the workability is inferior, a work of removal cannot be swiftly carried out. In addition, -:he support bodies (cores) such as H-shaped steels extracted out are consequently deformed, which are inappropriate for re-use.
Therefore, various methods for facilitating the foregoing extracting works have been conventionally proposed, which include (i) a method in which a lubricant such as wax or grease is preparatorily applied on a surface of an H-shaped steel, a method in which a water-absorbent resin is applied onto a surface of an H-shaped steel with use of an adhesive, (ii) a method in which a lubricating material is bonded on a surface of an H-shaped steel, and (iii) a method in which an H-shaped steel is covered with a covering member.
As the method of the above (i), the Japanese Publication for Laid-Open Patent Application No. 58715/1989 (Tokukaisho 64-58715 (date of publication: Mar. 6, 1989)) proposes that a surface processing agent for core-extraction use, which is made of a water-absorbent resin and a spreading agent such as a polyester-based resin, a vinyl-based resin, an acryl-based resin, or an urethane-based resin is used rather than the foregoing lubricant. The Japanese Publication for Laid-Open Patent Application No. 165615/1988 (Tokukaisho 63-165615 (date of publication: Jul. 8, 1988)) proposes a method in which a water-swelling film made of a water-absorbent resin and a volatile-film-forming resin such as natural rubber, synthetic rubber, or plastic is used, rather than the foregoing lubricant, so that frictional resistance upon extraction of a steel stock is reduced.
Furthermore, as the method of the above (ii), the Japanese Publication for Laid-Open Patent Application No. 185054/1994 (Tokukaihei 6-185054 (date of publication: Jul. 5, 1994)) proposes application of a sheet-like lubricating material made of superabsorptive fibers onto a surface of a steel stock. Further, for example, the Japanese Publication for Laid-Open Patent Publication No. 174418/1987 (Tokukaisho 62-174418 (date of publication: Jul. 31, 1987)) proposes that a lubricating tape made of a water-absorbent resin and a binder is used so that frictive resistance upon extraction of steel stocks is reduced.
Furthermore, as the method of the above (iii), the Japanese Publication for Laid-Open Patent Application No. 247549/1995 (Tokukaihei 7-247549 (date of publication: Sep. 26, 1995), corresponding to the European Patent Application No. 0663477A1 (date of publication: Jul. 19, 1995)) discloses a method in which a temporarily buried reinforcement is covered with a bag-shaped lubricating member composed of a polymer sheet which is produced by bonding a water-absorbent resin directly onto a substrate such as woven fabric or non-woven fabric without use of a bonding agent, so that frictive resistance upon extraction of the buried reinforcement is reduced.
However, the spreading agent contained in the surface processing agent which is proposed in the aforementioned Tokukaisho 64-58715, and the volatile-film-forming resin contained in the water-swelling film which is proposed in the aforementioned Tokukaisho 63-165615 are inferior in solubility in cement water contained in a hydraulic composition such as concrete, as well as inferior in swelling with respect to the same. Accordingly, both of the foregoing spreading agent and the foregoing volatile-film-forming resin hinder volume expansion of the water-absorbent resin upon its swelling by absorbing water. Thus, the foregoing surface processing agent and the foregoing water-swelling film have a drawback in that the water-absorbent resin cannot fully exhibit its absorbing property (performance) since the spreading agent and the volatile-film-forming resin thus coat surfaces of the water-absorbent resin, thereby hindering volume expansion of the water-absorbent resin. Furthermore, the water-absorbent resin contained in the conventional surface processing agent and water-swelling film is inferior in swelling by absorbing cement water. Moreover, a coating film obtained by applying the foregoing surface processing agent on a support body such as an H-shaped steel used as core, as well as the water-swelling film, since being inferior in flexibility and tenacity, tend to exfoliate from the support body (core) or become sticky, and to be damaged due to friction during application and construction works. Furthermore, in the case where the surface processing agent is applied to the support body (core) at a site of construction, there is a drawback in that labor, time, place, and the like for heating, melting, and applying the surface processing agent have to be prepared.
Therefore, the foregoing conventional surface processing agent and water-swelling film have drawbacks in that they do not exhibit satisfactory performance, and in that they yield only a poor effect for facilitating the works of extracting the support body (i.e., temporarily buried reinforcement) such as an H-shaped steel which has been buried as core.
Regarding the lubricating material disclosed in Tokukaihei 6-185054 and the lubricating tape disclosed in Tokukaisho 62-174418, since the superabsorptive fiber and the water-absorbent resin therein are inferior in water-absorbing swelling caused by absorption of cement water, the lubricating material and the lubricating tape only insufficiently facilitate the work of extracting the support body (i.e., temporarily buried reinforcement). The foregoing lubricating tape easily dissolves when the binder becomes in contact with water, resulting in that the water-absorbent resin tends to fall off. Furthermore, a surface of a steel stock to be buried is usually soiled with rust and dust, and this hinders the lubricating tape from adhering to the steel stock. Besides, cement water to which the lubricating tape tends to become in contact with, unexpected wetness or precipitation, or the like during this construction work also causes the water-absorbent resin to fall off and become lost. Therefore, the lubricating tape cannot fully exhibit its effect. Furthermore, binder thus dissolving causes steel stocks to easily slip, thereby producing dangerous circumstances in some cases, and further, in the case where steel stocks are piled in the open air, the lubricating tape cannot be applied onto the steel stocks when they are wet due to precipitation or the like. Thus, there are many limitations from the viewpoint of practical application thereof to actual construction works. On the other hand, since the swelling material is in the sheet form made of superabsorptive fiber, it further more easily absorbs water than the foregoing lubricating tape does. Therefore, the lubricating material tends to easily fall off and become lost, and moreover, since a surface of a steel stock to be buried is usually soiled with rust and dust, this hinders the lubricating material from adhering to the steel stock. Accordingly problems like the aforementioned ones arise.
Therefore, satisfactory performance cannot be obtained from any one of the foregoing conventional surface processing agent, water-swelling film, lubricating material, and lubricating tape, and accordingly, only a poor effect is achieved by any one of them for facilitating the work of extracting the support body (temporarily buried reinforcement) used as core out of the hardened body of the hydraulic composition.
Furthermore, the bag-shaped lubricating material disclosed by the aforementioned Tokukaihei 7-247549 is arranged so that the water-absorbent resin is directly and firmly bonded to a substrate without use of a bonding agent (in other words, monomers are made to adhere directly to the substrate, and polymerized on fibers of the substrate so as to be bonded thereto). A material which is soft and whose fiber restriction (entanglement and binding power of fibers) is small is adapted so as to be used as the substrate in the foregoing lubricating material. This is because, in the case where a substrate which is thick and strong is used, productivity of the resultant product (lubricating material) extremely lowers, as well as because, in the case where a substrate whose fiber restriction is great is used, the resultant product (lubricating material) has hard texture and is prone to wrinkles, thereby having lower quality. Accordingly, the product (lubricating material) according to the foregoing publication has lower strength. The conventional bag-shaped lubricating material using the substrate thus having lower strength is possibly damaged by external force which is exerted to the lubricating material at such occasions as when the lubricating material is applied to the support body so as to cover it, or when the support body is buried (driven) into the hydraulic composition poured into bore holes so that the support body serves as core. Thus, in some cases, it is impossible to sufficiently prevent the adhesion of the support body to the cured body of the hydraulic composition.
Therefore sought for is a technique for suppressing adhesion between the support body and the hardened body of the hydraulic composition such as cement composition and easily separating the hardened body and the support body, particularly a technique for extracting the support body buried in the hardened body therefrom in a more easily manner.
Incidentally, techniques currently put in practical application are, since no alternative techniques exist, only a technique in which a lubricant is made to adhere directly to a surface of a support body such as an H-shaped steel, and a technique in which a support body (core) is covered with a polyvinyl chloride sheet with lubricity, in spite of their drawbacks which include a drawback in that effects relating to facilitating the extraction and the construction are poor and a drawback in that sometimes a greater-scale extracting device than prearranged becomes required unexpectedly during an extracting operation.